Multivibrator circuit



WITNESSES: 5% W2 9%. f w I July 29, 1952 Filed Au 12, 1950 WZ'L 1m 35 il;

INVENTOR Lawrence H.Crondon.

Patented July 29, 1952 MULTIIVIBRATORI 'omom'r Lawrence ILCi-andon,Wilkinsburg, Pa., assignor to Westinghouse Electric Corporation, EastPittsburgh, P a., a corporation of Pennsylvania Application August 12,1950, Serial No. 179,057

My invention relates to electrical apparatus and particularly toelectronic circuitsof the multivibrator type.

Many electronic systems require a. source of sharp pulses of short timeduration, and having an essentially square wave form. A number ofmultivibrator circuits which exist in the prior art of which I am aware,attempt to produce such pulses. These circuits, however, leave much tobedesired in the wave form and amplitude of the output pulse.

It is,'accordingly, a broad object of my invention to provide animproved multivibrator circuit.

It is another object of my invention to provide a multivibrator circuitwhich will produce voltage pulses of short time duration having steeprise and decay characteristics, and having an amplitude substantiallyequal to that of the supply voltage.

In accordance, with my invention, I provide a multivibrator circuitcomprising a pair of electronic tubes, one of which. may be a triode andthe other a pentode. The circuit of my invention is arranged so as toprovide feedback from the triode, to the cathode, and the screen andsuppressor grids of the pentode, whereby voltage pulses having desirablecharacteristics including very short rise and decay times and relativelylarge amplitude are provided.

Other objects and advantages of my invention will appear from thefollowing description of a preferred embodiment, taken in connectionwith the accompanying drawing, in which the single figure is a schematicdiagram of a preferred embodiment of my invention.

The multivibrator circuit shown in the draw-- ing includes a pairofelectronic tubes, one of which may be a triode I I and the other apentode I3. The cathodes I5, II of these tubes are connected through acommon bias resistor III to ground 2|. The positive terminal 23 of adirect current anode potential source (not shown) is connected througha. first resistor 25 to the anode 21 of the pentode I3, and throughsecond and third resistors 29, 3| to the anode 33 of the triode II. Theanode 21 of the pentode I3 is connected through a capacitor 35 to thecontrol grid 31 of the triode II. A fourth resistor 39 is connectedbetween the control grid 31 and cathode I5 0! the triode II. The screengrid M of the pentode I3 is connected to the anode 33 of the triode II.The control and suppressor; grids 43, 45 of the pentode I3 are connectedto ground 2 I. A by-pass capacitor 41 is connected from the 'junction ofthe second and third resistors 29, 3|

;7 claims. (01. 250-27) -1 2 to ground 2|. application of trigger pulsesbetween the control grid 31 of the triode II and ground 2I. pulses aretaken from terminals 5| provided between the anode 21 of the pentode I3and ground 2|.

In the operation of the circuit, the triode II is normally conductiveand the pentode I3 is normally non-conductive. To get an output pulse, anegative trigger pulse is applied to the grid 31 of the triode II. Thisreduces the plate current of the triode II, which in turn decreases thevoltage drop across the cathode bias resistor I9. Reduction in voltagedrop across thecathode bias resistor I9 makes the pentode control andsuppressor grids 43, 45more positive with respect to the cathode I'I. Atthe same time the plate voltage on the triode II has increased which hastheeffect of making the pentode screen grid.

4| more positive with respectto the cathode I]. As a result of theseeffects which operate simultaneously, the pentode I3 becomessuddenlyconductive. The anode voltage of the pentode I3 is lowered,making the control grid 31 of the triode I I more negative. This actionis cumulative until the triode II is cut ofi and the pentode I3 is fullyconductive. The coupling capacitor 35 then begins to charge through thefourth resistor 39 making the control grid 31 of the triode II morepositive. This action continues until the cut-oif J point is reached, atwhich time the triode II again conducts. Current through the triode willthen increase the voltage drop across the cathode bias resistor I9 whichwill tend to make the pentode control andpsuppressor grids 43, 45 morenegative. At the same time, the plate voltage-on the'triode I I hasdecreased, which has the effect of making the pentode screen grid 4Imore negative with respect to the cathode II. These effects arecumulative until the pentode I3 is cut of! and the triode II is againfully conductive.

In the practice of my invention I have used the following circuitconstants with good results: pentode tube I3, type 6AG7; triode tube II,type 12AU7 (sections connected in parallel); first resistor 25, 22,000ohms; second resistor 29, 6,200 ohms; third resistor 3|, 2,800 ohms;fourth resistor 33, 100,000 ohms; cathode bias resistor I9, 500 ohms;coupling capacitor 35, 4 to 30 micromicrofarads; by-pass capacitor 41,0.5 microi'arad.

I am aware that some modifications of the circuit shown and describedcould be made without departing from the scope of my invention. Idesire, therefore, to be limited only insofar Terminals 43 are providedfor".

Outp t as is necessitated by the prior art and the spirit of theappended claims.

I claim as my invention:

1.'A multivibrator circuit comprising a first electronic tube having ananode, a cathode, and a control grid, a second electronic tube having ananode, a cathode, a control grid, a screen grid, and asu pressor-grid,abias'resistor connected between said cathodes and ground,meansconnected to supply anode potential to said tubes,

means coupling the anode of said second tube 1 to the control grid ofsaid first tube, a connection from the anode of said first tube to thescreen grid of said second tube, and connectionsirom l the suppressorand control grid of said s'econd tube to ground. r

2. A multivibrator circuit comprisinga first; electronic tube having ananode, a cathode, and

a control grid, a second electronic tube having i an anode, a cathode,a-lcontrol grid, a screen grid, and a suppressor grid, a bias resistor,con-.

nected between: said cathodes sand, ground-,- means connectedtosupply'anode potential to said tubes, means coupling theranode: of saidsecond ,tube to the control grid of said firsttube aconnection from theanode of said first tube to the; screen grid of said second ltd-be,connections from the suppressor and controhgridofrsaid second tube-toground, landimeans to apply .atrjigger pulse-to; th

' control electrodeofsaidrfirsttuhe.

35A "multivibra'tor: circuit. comprising a first normallyconductiv'eelectronic tube havingwzan.

anode, a: cathode and a; control, 1 electrode, a second normallynon-conductive electronic tube having' an anode, l aLcath'ode, control,screen, and suppressor 'grids, rneanscconnected. xtojsupply directcurrent anode potential to: said'itubes, con-.- duc'tors" connectingsaidz cathodes together and through a bias resistor ito ground,ymeanscou:

pling the anode of said;v second-tube to ;the.;ccn:- trol-grid of saidfirst tub'e; means connecting, the anode --of said first tube-to the:screen-;grid' of said second tube, conductors connecting ythe' controlgrid and suppressor grid of said ,second tube "to ground, and means forapplying :a.:-nega@-. tive trigger--pulse 'to the lcontrol grid; "ofsaid.

first-tube 1 V 4. multivibratorcircuitcomprising; .a first.

normally conductive electronic tube having: "an' anode, =a 'cath'ode',and a control electrode, :aisecond normally non conductive electronic"tube; havingamanede a cathode, control, screen, .and

suppressorgrids meansconnected to. supply direct" current "anodepotential to said tubes,:- conductors 'connecting said cathodes togetherand through -a bias resistor'to-g round', means-include ing a'fcapacitor for coupling the anode oil-said,

ond normally non-conductive electronic tube having an anode, a cathode,control, screen, and

"suppressor" grids, means connected to supply di- "rectcurrerit anodepotential to said tubes, conductors-connecting saidcathodes together andth-rough' -a bias'resistor to ground, a capacitor connected between theanode of said second tube and the control grid of said first tube, and aresis'tor connected between the control grid and cathode of said firsttube, means connecting the anode of saidifirst tube to the screen.rids-of said-seccndstube, c nd ctors; wnnectingthacontrol grid andsuppressor grid of said second. tube,

to ground, and means ior applyi a negative tri serzpul e tothecontrolgr-idof said first tube 6.A' multivibrator circuit, comprisinga first electronic tube having an anod a cathode; and a controlgrid,.asecond electronic tubeihaving.

an anode, a cathode, 'control,1,.v screen, and suppressor grids, acommon-cathode bias resistor, and coupling means connected toiprovideieed back voltage from said-;first=:.tube to the control,

screen; andisupnressorsgrids 'of; said second-:tube-..

7;.A multivibrator 'circuihcomprising. a first electronic tube having:an anode, a cathodeyand a 7 control grid, 11a se,cond,-:,electronic.tube having. an anode, ,ia. cathode,: a icontrol grid, a' -screen.grid, and agsuppressor ;grid,;.a-bias: resiston; means for connectingsaid cathodes through. said-biasg resistorto a point :of: referencepotential,:mea'ns coupling the anode of .said; second :tube to; thevcontrol grid f said :fir'stn tube; means ..'coupling: theq'anode ofsaidfirst tube to theescreeni-grid; of.isaid secondmube, and ;meanscoupling-the control and suppressor: grids of saidsecondztubeand; thecontroli-gridvofcsaidifirst tube to i-saidpoint ofpreferencezpotential.1 .1

LAWRENCE-H.- oRANDoNf I]REFEnENcEs.-jc1frED The f'ollowing referencesare of fileof" this patent: 7

UNITEDLSTATESTPATENTS Number, 7 .Name Date 2,330,638: :Stratton inn-risseptlaasaiega record in the

